In recent years, there is an increasing use of real-time applications including streaming distribution, such as VoIP (Voice over Internet Protocol) and VoPN (Voice over Packet Network), which perform transmission and reception of audio and image data between devices over a communication network such as an IP network. When a real-time application is used, the reproduction quality in reproducing audio and video data received on the application is influenced by the state of the IP network. Therefore, a guideline determined by the Ministry of Internal Affairs and Communications defines that providers of IP phone services should maintain certain communication quality for their services.
However, since a VoIP network including a plurality of communication networks such as an IP network and a public network, which provides IP phone services, is generally built in a multi-vendor environment, it is difficult to secure and evaluate the transmission quality over the VoIP network. It is therefore necessary to provide an evaluation method for predicting communication quality between communicating terminal devices making a call, namely end-to-end communication quality, by simulating the characteristics of the communication network representing the communication state over the VoIP network, and actually making a call between the terminal devices. A method for simulating the communication state to evaluate the quality of such communications is disclosed, for example, in Japanese Patent No. 2997607.